Investigations of a new pathway for catabolism, recently discovered for phenylalanine and tyrosine in Trichosporon cutaneum, will be extended. Substrate specificities and patterns of derepression will be established for enzymes concerned with the catabolism of these amino acids, and of aromatic acids related to them. A new enzyme responsible for initiating the degradation of L-phenylserine in a gram-positive soil bacterium will be purified and examined. Studies relating to the mechanism of action of bacterial isomerase for maleylacetoacetic acid will continue.